1. Field Of The Invention
This invention relates generally to a process, apparatus, and composition for removing moisture and oxidant impurities from hydrogen selenide and/or hydrogen telluride.
2. Description Of The Art
Hydrogen selenide and hydrogen telluride are widely used in the semiconductor industry for the manufacture of microcircuitry devices, as source reagents for elemental selenium and tellurium, respectively. Specifically, these source reagents are used as n-type dopants for the manufacture of n-type semiconductors and infrared diodes.
In these applications, hydrogen selenide and hydrogen telluride are utilized in gaseous form and frequently contain undesirable contaminants, such as moisture and oxidants, e.g., water and oxygen. If such contaminants are present, they will be incorporated in the structure of the microcircuitry device. Such impurities, when introduced onto the semiconductor chip during its manufacture, tend to produce localized defects in the crystalline structure, which may themselves be electrically active, which may then propagate to produce an undesirable epitaxy, and render the chip deficient or even useless for its intended purpose.
Hydrogen selenide and hydrogen telluride are extremely difficult to purify because of their high reactivity and toxicity. Due to their high reactivity, these materials react detrimentally with many otherwise potentially useful scavengers, to poison the active sorption sites of such materials.
Insofar as we are aware, the prior art has not provided any suitable means or method for highly effecient purifying hydrogen selenide and hydrogen telluride, to remove moisture and oxidant impurities therefrom, and yield a purified effluent containing less than 1 part per million by volume of contaminant in the treated product.
Japanese Kokai Tokkyo Koho JP 60/222127 discloses the thermal decomposition of trimethyl aluminum to deposit elemental aluminium on a glass substrate, e.g., glass beads, following which the aluminum coating is reacted with arsine to form a scavenger for water and oxygen. Such method is not useful in application to the drying of hydrogen selenide or hydrogen telluride, however, since free arsine would be formed as a reaction product of such scavenger with the hydrogen selenide or hydrogen telluride, and such reaction product would contaminate the treated gas stream.
U.S. Pat. No. 4,603,148 to G. M. Tom discloses a macroreticulate polymer scavenger for removing moisture and oxidant impurities from inert fluids such as aliphatic hydrocarbons, olefins, and gases including nitrogen, argon, helium, xenon, hydrogen, carbon tetrafluoride, ammonia, and silane. The macroreticulate polymer backbone of the scavenger has bonded thereto a plurality of functional groups of the formula: ##STR1## where: Ar is an aromatic hydrocarbon radical of 1 to 3 rings; R.sub.1 and R.sub.2 are each independently hydrogen, C.sub.1 -C.sub.12 alkyl, methylene-bridged benzophenone, methylene-bridged fluorenone, or alkali or alkaline earth metal salts of such benzophenone or fluorenone radicals; and M is lithium, potassium, sodium, alkyl magnesium, or alkyl zinc, the alkyl substituents being C.sub.1 -C.sub.12 alkyl. Within the pores of the macroreticulate polymer is a metallating agent selected from the group consisting of alkyl lithium, alkyl sodium, alkyl potassium, dialkyl magnesium, alkyl magnesium halilde, and dialkyl zinc, wherein the alkyl moiety is C.sub.1 -C.sub.12 alkyl; alkali or alkaline earth metal salts of benzophenone; and alkali or alkaline earth metal salts of fluorenone.
The macroreticulate polymers which may be employed in this scavenger include those disclosed at column 3, line 60-column 4, line 6 of the Tom patent, with macroreticulate poly(styrene-divinylbenzene) being described as a preferred macroreticulate polymer for such purpose.
Among the Lewis acid and oxidant impurities for which the macroreticulate polymeric scavenger of this patent is disclosed to be effective, are oxygen, water, alcohols, phenols, aldehydes, ketones, carboxylic acids, carbon dioxide, carbon monoxide, alpha-acetylenes, allene, conjugated dienes, peroxides, sulfur compounds, and the like (column 5, lines 12-17).
The scavenger materials disclosed in U.S. Pat. No. 4,603,148, while generally effective in removing water from the fluids described hereinabove, are not suitable for the purification of gaseous hydrogen telluride or hydrogen selenide, because the active sites of such scavengers would be quenched instantly by the hydrogen telluride or hydrogen selenide.
This is unfortunate, since as the macroreticulate polymer disclosed in this patent represents a highly efficient configuration for contacting fluids to remove impurities therefrom. The macroreticulate polymer can readily be provided in the form of beads of high surface area, e.g., greater than 500 meters.sup.2 /gm, with a plurality of highly efficient sorptive sites for removing impurity constituents from numerous fluids.
Accordingly, it is an object of the present invention to provide a highly efficient composition, apparatus, and process for removal of moisture and oxidant impurities from gaseous hydrogen telluride and/or hydrogen selenide.
It is a further object of the invention to provide a scavenger of the type generally described above, having a high capacity for impurities, and which does not introduce any significant amount of impurities into the treated hydrogen selenide and/or hydrogen telluride product gas.
Other objects and advantages of the invention will be more fully apparent from the ensuing disclosure and appended claims.